Buoy Suspension Fractionation System

ABSTRACT

A separator that uses centrifugation to fractionate a suspension such as blood comprises a separation container and a buoy. The buoy is carried in the separation container and has a tuned density that is configured to reach an equilibrium position in a suspension. The guide surface is carried on the buoy upper surface and is inclined to an accumulation position near a buoy perimeter. The buoy suspension fractionation system can be used in a method of isolating a fraction from a suspension, and in a method for re-suspending particulates for withdrawal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No. 13/198,038 filed on Aug. 4, 2011, which is a continuation of U.S. patent application Ser. No. 12/101,586 filed Apr. 11, 2008, now U.S. Pat. No. 7,992,725 issued on Aug. 9, 2011, which claims the benefit of U.S. Provisional Application No. 60/911,407 filed on Apr. 12, 2007. The disclosures of the above applications are incorporated herein by reference.

FIELD

The present teachings relate to a separator that uses density differences to fractionate a suspension such as blood.

BACKGROUND

Clinicians have identified a wide range of therapeutic and laboratory applications for autologous isolated fractions, such as platelet concentrate, platelet-poor-plasma, and stromal cells, of suspensions such as blood, bone marrow aspirate, and adipose tissue. Clinicians generally prefer to draw and fractionate the autologous suspension at the point-of-care. Point-of-care fractionation can reduce the need for multiple appointments to draw and fractionate the autologous suspension which can be costly and inconvenient. Additionally, point-of-care preparation reduces potential degradation of the autologous suspension that can begin once the autologous suspension is removed from a patient. Point-of-care fractionation systems should be easy to operate to reduce the need to provide clinicians with extensive instruction, quick so the therapeutic fraction can be isolated and administered during a single patient visit, efficient to effectively isolate the fraction to a desired concentration, and reproducible to operate over wide variations in suspension characteristics. An example of a buoy based suspension fractionation system is shown in Biomet Biologics, Inc. international brochure entitled “Gravitational Platelet Separation System Accelerating the Body's Natural Healing Process.” 2006

SUMMARY

A buoy suspension fractionation system comprises a separation container and a buoy. The separation container defines a volume enclosed by a container wall, a container bottom, a container top and an access port to access the volume. The buoy is carried in the separation container and has a tuned density that is configured to reach an equilibrium position in a suspension. The buoy comprises a buoy upper surface and a buoy sidewall defining a height, a transverse dimension, and a perimeter. The buoy further comprises a guide surface and a collection space above the buoy upper surface. The guide surface is carried on the buoy upper surface and is inclined to an accumulation position near the buoy perimeter. The buoy suspension fractionation system can be used in a method of isolating a fraction from a suspension, and in a method for isolating a fraction and re-suspending isolated particulates for withdrawal.

BRIEF DESCRIPTION OF THE DRAWINGS

The present teachings will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1 is an environmental view of a fractionation device including a suspension fractionated during the centrifuge process;

FIG. 2 is an environmental view of a suspension being added to a fractionation device;

FIG. 3 is an environmental view of a centrifuge;

FIG. 4 is an environmental view of a first fraction being removed from the fractionation device;

FIG. 5. is an environmental view of the fractionation device being agitated to re-suspend a portion in a second fraction;

FIG. 6 is an environmental view of the second fraction being removed from the fractionation device;

FIG. 7 is an environmental view of a therapeutic application of the second fraction;

FIG. 8 is an environmental view of a separation container and a buoy;

FIG. 9A is a plan view of a buoy according to various embodiments;

FIG. 9A1 is a plan view of a buoy at a selected transverse plane;

FIG. 9A2 is a plan view of a buoy at a selected transverse plane;

FIG. 9B is a cross-sectional view of the buoy of FIG. 2A;

FIG. 10 is a perspective view of a buoy, according to various embodiments;

FIG. 11A is a perspective view of a buoy, according to various embodiments;

FIG. 11B is a perspective view of a buoy in a closed position, according to various embodiments;

FIG. 12 is a perspective view of a buoy, according to various embodiments;

FIG. 13 is a perspective view of a buoy, according to various embodiments;

FIG. 14 is a plan view of a buoy, according to various embodiments;

FIG. 15 is a plan view of a buoy, according to various embodiments;

FIG. 16. is a plan view of a buoy, according to various embodiments;

FIG. 17 is a plan view of a buoy, according to various embodiments;

FIG. 18 is a plan view of a buoy, according to various embodiments;

FIG. 19 is an environmental view of a selected component being withdrawn from a separation device according to various embodiments; and

FIG. 20 is a kit according to various embodiments, for separation and extraction of a selected component of a suspension.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

FIG. 1 shows a buoy suspension fractionation system 10, according to various embodiments that can be used in a clinical or laboratory environment to isolate fractions from a suspension or multi-component material removed from a patient or a preparation of extracted or excised material from a patient. The suspension can include a sample of blood, bone marrow aspirate, cerebrospinal fluid, adipose tissue, and the isolated fractions can include platelets, platelet poor plasma, platelet rich plasma and stromal cells. The isolated fractions can each have equilibrium point or positions within the separation container that are achieved when separation has occurred. For example, a buffy coat of whole blood may have an equilibrium position above that of the red blood cells when a sample of whole blood is separated.

Isolated fractions can be used in a variety of clinical applications, animal applications, and laboratory applications. Some of the clinical applications include peripheral vascular disease, orthopedic surgery, plastic surgery, oral surgery, cardio-thoracic surgery, brain and neural procedures, and wound healing. Laboratory applications include isolating, creating or synthesizing therapeutic materials or materials for analysis from fractions produced by the fractionation system.

Although the fractionation system 10 can be used allogeneically, such as with pooled blood, the fractionation system 10 can be used autologously to reduce risks of potential incompatibility and contamination with pathogenic diseases. Also, other autologous materials can be used including cerebrospinal fluid, cerebrospinal fluid can be obtained via a spinal tap or other appropriate collection procedure. A general description of a fractionation system is provided in a Biomet Biologics, Inc. international brochure “Gravitation Platelet Separation System Accelerating the Body's Natural Healing Process” (2006) and a description of a therapeutic procedure using platelet concentrate is shown in a Biomet Biologics, Inc. international brochure “Shoulder Recovery with the GPS Platelet Concentration System” (2004), incorporated herein by reference.

FIGS. 2-7 show exemplary fractionation system operational steps for a clinical therapeutic application embodiment. The operational steps begin in FIG. 2 by inputting autologous (although pooled blood can be used) whole blood into the fractionation system 10, via an access port 22. The fractionation system 10 is placed into a centrifuge 23 in FIG. 3 and spun about five minutes to about twenty minutes at a rate of about 320 rpm to about 5000 rpm (this speed may produce a selected gravity that may be approximately 7.17×g to about 1750×g (times greater than the normal force of gravity)). The first fraction or top fraction 308 (FIG. 1), which can be platelet-poor-plasma according to various embodiments including from a whole blood sample, is shown being removed in FIG. 4. The fractionation system 10 is agitated in FIG. 5 to re-suspend at least a portion of a second fraction 310, which can be platelet-rich-plasma or platelet concentrate, according to various embodiments including from whole blood fractionation. The second fraction is removed from the fractionation system 10 in FIG. 6. Finally, the second fraction is applied as part of a therapy, such as shown in FIG. 7 to treat elbow tendonitis. The second fraction can be injected into a selected portion of an elbow 29 to treat tendonitis.

It will be understood that the buoy 30 can be altered depending upon the material placed in the container 12. For example, if neural stem cells are to be separated from cerebrospinal fluid then the buoy 30 can have a density to allow collection of the neural stem cells in the collection area 52 of the system 12. The collected neural stem cells can also be applied for therapeutic reasons or used in laboratory study, isolation, culture, etc.

Returning reference to FIG. 1 and with additional reference to FIGS. 8-9B, the suspension fractionation system 10 comprises a separation container 12 and a buoy 30. The separation container 12 can be a separation tube having a container wall 16, a container bottom 18, and a container top 20 enclosing a volume 21 that can be accessed by one or more access ports 22, 26, 27, and a container vent 31. The container 12 may be formed of any appropriate material, such as the Cryolite Med® 2 material sold by Cyro Industries Evonik Degussa Corp. The container 12 can be about 50 mm to about 150 mm in height, including about 102 mm in height. The container 12 can have an internal diameter of about 20 mm to about 40 mm, including about 25 mm to about 35 mm and define a volume of about 30 ml to about 100 ml, including about 30 ml to about 60 ml. The separation container 12 can have any appropriate shape, such as an oval, provided the buoy 30 is shaped to conform to the separation container 12. Though not particularly illustrated, the separation container 12 can also have more than one compartment, such as a separation tube and an area to transfer tube contents away from the separation tube 12. For example, a separate compartment can be formed to house the assembly of the buoy 30 and isolator 32 separate from another area.

The various ports 22, 26 and 27 can be provided to allow access to any appropriate compartment of the container 12. The access ports 22, 26, 27 can be any means that allow communication from outside the separation container 12 to the separation container volume 21 such as a Luer lock port, a septum, a valve, or other opening. The container vent 31 allows movement of air between the inside and outside the separation container 12 to equalize pressure when suspension in introduced into or withdrawn from the separation container 12. The container vent 31 can include a vent filter 31 a to serve as a sterile barrier to allow air to enter the separation container 12 while preventing undesired materials from entering the separation container 12.

When the separation container 12 is at rest, a buoy perimeter 30 a and the container wall 16 can be dimensioned to form an interference fit to hold the buoy 30 at a position in the separation container 12. When the separation container 12 is centrifuged, the buoy perimeter 30 a and the container wall 16 have clearance allowing the buoy 30 to move within the separation container 12 and a material to pass between the buoy perimeter 30 a and the container wall 16. For example, the container 12 can compress axially to increase its internal diameter. Alternatively, the buoy 30 could have an opening (e.g. FIG. 16), such as a centrally or internally located opening 176 or a peripheral channel 168 a (FIG. 13) running the height of the buoy, which would allow a material to move through the buoy.

The buoy 30 is carried in the separation container 12 and has a tuned density that is configured to reach a selected equilibrium position in a suspension. The buoy can have its density tuned in the range from about 1.0 g/cc to about 1.10 g/cc, such as about 1.06 g/cc. The buoy 30, according to various embodiments, can be formed to include the tuned density and can be formed of one or more materials to achieve the tuned density.

For example, the density of about 1.06 g/cc can position the buoy 30, or a selected part of the buoy 30 including the collection area 52, at an equilibrium position of a buffy coat of a separated whole blood sample. In a further example, the density can also be tuned so that the collection area 52 is near an equilibrium position, such as where neural stem cells collect in a selected suspension. Regardless of the density of the buoy 30, it can be selected to position the buoy 30 at an equilibrium position of a selected material.

As illustrated in FIG. 1, the collection area 52 is positioned within the container 12 after a separation procedure has occurred. The collection area, defined relative to the buoy 30, is positioned at the equilibrium position of the separated or isolated fraction 310 in the container. The equilibrium position of a selected fraction can be defined as its position within the container relative to other fractions in the container of a separated sample or material. The equilibrium position can also be defined relative to the axis X of the buoy 30 or the container 12. The equilibrium position, however, may depend upon the amount of the sample of the amount of a selected fraction within a sample. According to the illustration in FIG. 1, the equilibrium position of the fraction 308 is above or nearer the top 20 of the container 12 than the equilibrium position of the fraction 310. Thus, the buoy 30 can be tuned, such as including a selected density or specific gravity, to position the collection area 52 relative to an equilibrium position of any selected fraction.

The buoy comprises a buoy upper surface 48 and a buoy sidewall 38, 40 defining a height H1, H2, a transverse dimension at planes A₁, A₂, and a perimeter 30 a, discussed further herein. The buoy further comprises a guide surface 42. In some embodiments, the buoy can further comprise a collection port 50 and a precision collection region 44. The collection port 50 communicates with the access port 27 and communicates with a collection space 52 above the buoy upper surface 42 and can be located near the buoy perimeter 30 a. In some embodiments, the collection port 50 is not carried on the buoy, but rather the collection port is a withdraw device such as a syringe that is inserted through an access port or top of the tube 12.

With reference to FIG. 9A, the buoy 30 has a first height dimension H1, a second height dimension H2, a maximum width or transverse cross sectional area W1 at plane A1, a second width or transverse cross sectional area W2 at plane A2, a guide surface angle ∝, and precision collection area 44 including a surface 46 defining a precision collection region angle β. The height of the buoy 30, according to various embodiments, can be defined relative to a central axis X, which can also be a longitudinal axis X of the container 12. The sidewalls of the buoy 30 and the container 12 can also be substantially parallel to the axis X. Although certain dimensions are shown in FIG. 9A, the buoy perimeter could be shaped differently provided the perimeter conforms to the separation container 12.

The guide surface 42 is carried on and/or defined by the buoy upper surface 48 and is inclined to an accumulation position at or near the buoy perimeter. The guide surface 42 serves as a guide means for conveying particles down an incline toward an equilibrium interface or collection region. The guide surface 42 can be inclined relative to the buoy sidewall 38 height for a distance of more than one-half the buoy transverse dimension or width W1, such as about two-thirds the buoy transverse dimension, and in various embodiments the guide surface can be inclined relative to the buoy sidewall 38 substantially throughout a length of the guide surface 42.

The guide surface 42 can be substantially planar and can have an average angle in the range from the minimum for particulates to move down the guide surface, regarding blood platelets, for example, about 10 degrees to about 60 degrees. For example, angle

can be about 5 degrees to about 89 degrees, or greater, including about 30 degrees to about 89 degrees. Angle

can, exemplary, be exactly or about 60 degrees in various embodiments. In some embodiments, the guide surface can include contours defined in the guide surface with multiple angles such as shown in FIGS. 10 and 12. For example, in FIG. 10, a buoy 80, according to various embodiments, can include two guide surface contour walls 96, 98 to assist in defining a guide surface 100. The two walls 96, 98 can define a trough that extends a selected distance across the guide surface 100, such as more than two thirds. The trough can define an area of the guide surface that is lower than the surrounding area. A contoured precision collection region 92 can also be defined that communicates with a port 94. In FIG. 12, a buoy 140 can include a guide surface 152 that includes two inclined sides 154, 156 angled towards a selected region, such as a center of the guide surface 152. The entire guide surface can also be inclined towards a collection port 158, in an amount as discussed above.

In various embodiments, as exemplary illustrated in FIGS. 9A, 9A1, and 9A2 the different buoy transverse cross-sectional areas W1, W2 can be defined at various planes, such as A₁, A₂, etc. As illustrated, various transverse cross-sectional areas can be defined by the buoy 30 due to the angled top wall 42. The transverse cross-sectional areas defined at the various planes A₁, A₂ can be positioned at selected locations based upon characteristics of the buoy 30, such as density. The height H2, angle

, etc. The width dimension can be 1 inch to about 2 inches including about 1.347 inches (about 25 mm to about 51 mm, including about 34.21 mm) for W2. The dimension of W1 can depend upon the selected location of plane A1. These dimensions can achieve various areas depending upon the geometry of the buoy 30. Nevertheless, the area at plane A2 can be substantially similar to an area at a transverse plane within the container 12.

In use, the substantially maximum transverse cross-sectional area W1 of the buoy 30 can be positioned at a selected location. As illustrated in FIG. 9A1, the maximum cross-sectional area is at plane A₁. The plane A₁ can be positioned at or near a selected equilibrium interface, in use. The position of the plane A₁ is selected by selecting a density of the buoy 30 and the known or estimated density of the material into which the buoy 30 is positioned. The buoy's maximum transverse cross-sectional area near the intended or selected interface results in a substantially maximum change in displacement of the relative volume of a fraction below the equilibrium interface and substantially maximum change in displacement of a fraction above the equilibrium interface relative to change in the axial orientation of the buoy relative to the interface. This can improve fractionation isolation by ensuring that the maximum transverse cross-section displaces a maximum amount of area within the container 12 at the selected interface. For example, more than 90% of a whole blood's platelets can be isolated.

Thus, in applications involving suspensions, such as whole blood, which may be variable in composition between samples, sample density variation will result in minimal variation in the axial orientation of the buoy relative to a selected equilibrium interface. The minimal variation in axial location of the buoy 30 in the container 12 is based at least in part on the maximum displacement of a material in the container at the maximum transverse cross-section of the buoy 30. In other words, for each small variation of axial location of the buoy 30, a maximum displacement occurs. In selected uses, the buoy's maximum cross-sectional plane A₁ is provided at a selected location and the minimal axial variation helps to ensure the plane A₁ is properly placed.

Additionally, at or near the buoy's maximum transverse cross-sectional area, the cross-sectional area of the fractionated material is near minimal. Simply, within the container 12 at a selected position if a maximum transverse cross-section of the buoy 30 is at a selected position, then a relatively minimal amount of other material can be present at the same location. In combination, the minimization of cross-sectional area of fractionated material and minimization of variation of axial orientation of the buoy in relation to an equilibrium interface results in minimization of variability of fractionated material volume near the interface.

The precision collection region 44, 92 (FIGS. 9A, 9B, and 10) can be interposed between the guide surface and the accumulation position at or near the buoy perimeter. The precision collection region 44, 92 serves as a precision collection structure for collecting a precise, high yield and/or pure amount of a selected fraction. The precision collection region 44, 92 can be raised or lowered in relation to the buoy perimeter to vary the fraction in the collection region without the need to make substantial changes to other buoy design features. In other words, the dimension H1 can be changed. Generally, the height H2 can be about 2.5 mm to about 5.1 mm. The height H1 will generally be constrained by the height H2 and the angle

. According to various embodiments, the precision collection region 44 is shown in FIG. 9A formed at an angle β in relation to the sidewall 40. The angle β can be any appropriate angle such as about 10 degrees to about 60 degrees, including about 45 degrees. According to various embodiments, the precisions collection region 92 can be contoured, FIG. 10.

According to various embodiments, an isolator 32, is coupled to the buoy 30. The combination of the isolator and buoy, according to various embodiments, can also be referred to as a separation assembly member. Exemplary isolators 82, 122, 170, 180, 190 are illustrated coupled to exemplary buoys 80, 120, 140, 160, 182, 192. The isolator 32, for example, provides a means for creating the collection compartment 52 and comprises one or more spacers 58, 60 to position the isolator 32 apart from the buoy 30 to create the collection compartment 52. A withdraw port 70 can be carried on the isolator 32 communicating with the withdraw port 27 and the collection port 50. The spacer 58, 60 can also serve as a conduit 68 between the collection port 50 and a withdraw or withdraw port 27. The withdraw port 27 serves as a structure for withdrawing the isolated or second fraction 310 from the collection compartment 52.

The isolator 32 can be configured from a material with a lower density than the buoy 30, such as a density of about 1.0 g/cc or less. A volume of the isolator 32 can be substantially less than a volume of the buoy 30. The isolator 32 can be configured so the isolator volume and the buoy volume combined below a selected equilibrium interface are greater than the isolator volume and the buoy volume combined above the equilibrium interface. As discussed above, an equilibrium interface can include a position relative to the platelet concentrate or buffy coat from a centrifuged whole blood sample, such as at or just below the platelet concentrate or buffy coat. By configuring the isolator 32 and buoy 30 with more volume below the equilibrium interface than above the equilibrium interface, the buoy 30 operates in a more repeatable manner even between a wide range in variations in compositions such as whole blood where the variability in density of a more dense fraction (e.g. red blood cells) is less than the variability in density of a less dense fraction (e.g. plasma). For example, the make up of a whole blood sample from one patient to the next can be markedly different.

Between individual patients, the density of the red blood cell or erythrocyte fraction of a whole blood sample can generally vary less than the density of a plasma or serum portion of a whole blood sample. Therefore, positioning a greater volume of the isolator and buoy within the denser fraction can assist in having highly repeatable and highly efficient collection or separation of a whole blood sample. The height H2 can be varied or selected to ensure a maximum or selected volume of the isolator and buoy are positioned within the denser fraction of the whole blood sample.

According to various embodiments, the isolator may include various features. An isolator 122 can be configured to move relative to a buoy 120, as illustrated in FIGS. 11A and 11B. The isolator 122 can move along a column or spacer 132 in the direction of arrow 123 during extraction of a selected fraction. The isolator 32, 82 can also be substantially uniformly thick or vary in thickness 122, 180, 190.

An isolator 170 can include collection openings 174 (FIG. 13). The isolator 32 can also include a collection vent 67 (FIG. 9A), which can also include a collection valve, a collection passage, or a collection vent tube or passage 203. The collection openings 174 can reduce the distance particles, such as platelets which are fragile and adherent, travel to reach a guide surface 162 and reduce the time that particles are in contact with surfaces. Various types of collection openings can be used.

The collection openings 174 can be sized to permit selected particles to pass yet sufficiently small so suspension fluid tension maintains adequate isolation of the collection compartment. The collection openings can also include various valves such as a duck bill or flapper bill which can open under certain conditions and close under others. A collection valve can be interconnected with any appropriate portion such as with a collection port 70 or passage 68.

The collection vent passage 67 through the isolator 32 equalizes pressure when fluid is withdrawn from the collection area 52. The spacer 58 can serve as a conduit for the collection vent passage 67, the collection port 50, or both. The collection valve communicates with the collection vent passage 67 to control collection vent passage 67 operation and close the collection vent passage 67 during re-suspension agitation. The collection vent tube 203 communicates with the collection vent passage 67 and air. The air can be the air above the collection area 52 (i.e. a portion of the suspension above the isolator 32 has been removed) or through an opening 205 in the container wall and generally through a sterile barrier (e.g. a sterile foam filter). The collection vent tube 203 allows removal of fractionated suspension in the collection compartment without the need to remove the fraction, such as plasma, above the isolator 32. Although, without a collection vent tube 203, the fraction above the isolator could be removed and the collection area could be vented to the area above the isolator.

Various embodiments further comprise a mechanical agitator 130 carried in a collection compartment 128 (for example FIGS. 11A and 11B).

The isolator 122 is moveable relative to the buoy 120. The isolator 122 can be in an open position after centrifugation of the separation container. During removal of material from the collection compartment through the collection port 134, the isolator 122 can move in the direction indicated by arrow 123 toward the buoy 120 to decrease or close the volume of the collection compartment 128.

The buoy 30 can also be formed in a plurality of selectable sizes, having different dimensions, such as those illustrated in FIG. 9A. The axial dimensions of the buoy 30 can be selected to achieve an appropriate displacement of the suspension in the container 12, especially after fractionation has occurred. Angle

, defined between the outer edge 38 and the surface 42 can be any selected angle. For example, angle

can be about 30 degrees to about 89 degrees, including about 60 degrees. The angle

can generally be created to be as small as possible to allow a steep angle of the surface 42 towards the inlet port 50 that will not damage the material being collected within the collection space 52. As discussed above, the height H2 can be selected to determine or select the amount of the buoy 30 positioned within a selected fraction, such as a dense fraction, of a sample separated within the separation system. Height H2 can be about 0.1 inches to about 0.2 inches, including about 0.18 inches (about 2.5 mm to about 5.1 mm, including about 4.57 mm). An exemplary height H2 is 0.1795 inches (4.559 mm), depending upon selected applications, the size of the separation system, and other selected factors. Nevertheless, the height H1 is generally defined by the height H2 and the angle

. Height H1 can be about 0.8 inches to about 1.2 inches, including about 1 inch (about 20 mm to about 30 mm, including about 25 mm). An exemplary height H1 can include 1.0 inches (25 mm). The positioning of the collection area 52, including the inlet port 50, can be based upon the height H2 and how the buoy 30 interacts with the material into which it is positioned, via the height H2.

A buoy 182, as illustrated in FIG. 17, can include an isolator 180 positioned relative thereto. The isolator 180 can include a center placed substantially over a center of the buoy 182. The center of the buoy 182 and the isolator 182 can both be defined by peaks or apexes 184 and 186, respectively.

A buoy 192, as illustrated in FIG. 18, can also be positioned relative to an isolator 190. The buoy 192 can include an apex 194 near a center of the buoy 192 and the guide surface extending from an edge of the buoy 192 to a second edge of the buoy 192. The isolator 190 can also include an apex 196 generally near its center. The isolator 190 can also include a surface 198 that extends from one edge of the isolator to another edge of the isolator 190.

The isolators 180, 190 can act substantially similar to the isolator 32, discussed above. The isolator 180, 190 can define an angle between an apex or the withdrawal port 70 and an outer edge of the isolators 180, 190. The upper surface of the isolators can include an angle to assist in directing a selected material, such as a platelet fraction of whole blood sample, to the collection area or surface 42 of the buoys 182, 192. Generally, the isolators 180, 190 can include a height or volume to substantially minimize the volume of the isolator 180, 190 relative to the buoys 182, 192. As discussed above, this can assist in positioning the buoys 182, 192 relative to a dense (e.g. red blood cell) fraction of a whole blood sample. The angle of the isolators 180, 190 and the height of the isolators 180, 190 can be selected to provide for a minimal distance of travel or least disturbance of a selected collected fraction of a material, such as a whole blood sample.

As discussed above, the buoy suspension fractionation system 10 can be used in a method of isolating a fraction from a suspension. The separation container 12 can be centrifuged for a period that is appropriate for the suspension. The buoy 30 in the separation container 12 is allowed to reach an equilibrium position within the formed fractions. Typically, the buoy moves from the separation container bottom to an equilibrium position within and/or between the fractions. In some embodiments, the buoy 30 is configured with the transverse dimension cross-sectional area of the buoy near the equilibrium interface to be substantially the buoy's maximum transverse cross-sectional area A₁, as illustrated in FIG. 1. As discussed above, the design of the buoy can be determined to position a maximum cross sectional area of the buoy within a selected fraction, such as the red blood cell fraction, of a whole blood sample. The positioning of the buoy can be based upon the density of the buoy which is determined from the density of a selected fraction, such as a red blood cell fraction. Therefore, the buoy can be created or formed to include a density to substantially position it within a red blood cell fraction, for example, of a sample to be separated. For example, the buoy can have a density of about 1.010 g/cc to about 1.1 g/cc. Exemplary densities include about 1.058 g/cc to about 1.070 g/cc, including about 1.064 g/cc. Such a buoy design effects a substantially maximum change in displacement of a volume of fractionated suspension below an equilibrium interface and effects a substantially maximum change in displacement of a volume of fractionated suspension above the equilibrium interface relative to the axial displacement of the buoy resulting in more precisely controlling the selected fraction isolation. As discussed above, the buoy, according to various embodiments, has a maximum cross section at a selected region. Positioning a maximum cross section within a selected fraction or area of a sample will maximum displacement of the sample relative to the buoy do to the maximum cross section of the buoy. In other words, by positioning the biggest portion of the buoy within a selected sample the biggest portion of the sample is displaced because of the displacement of the buoy.

Particulates are concentrated using a guide surface 42, 90, 138, 152, 162 of the buoy that is inclined to an accumulation position near a perimeter of the buoy. The guide surface can be inclined relative to the buoy sidewall substantially throughout a length of the guide surface. The guide surface can be defined by or positioned near the top wall of the buoy.

The particulates are conveyed along the guide surface of the buoy to a collection space. The particulates can be conveyed along a substantially planar path to the collection space. According to various embodiments, however, the guide surface can also include multiple angles 42, 44 and 152, 154 and/or contours 96, 98. The particulates can be selected from the group consisting of platelets, stromal cells, white blood cells, or the like.

A desired fraction is withdrawn from the collection space through an access port. In some embodiments, the desired fraction can be withdrawn from the collection space by tipping the separation container and pouring the desired fraction out through an access port or out through the container top. This is especially true when only the buoy 30′, 30″, 30″′ is present (FIGS. 14, 15, and 16).

In some embodiments, the method of isolating a fraction can further comprise isolating an isolated fraction in a collection compartment between the guide surface of the buoy 30, 80, 120, 140, 160, 180, 190 and an isolator 32, 82, 122, 142, 162, 182, 192 coupled to the buoy and withdrawing the isolated fraction through a withdraw port through the isolator.

The buoy suspension fractionation system can be used in a method of isolating and re-suspending particulates for withdrawal. The method begins by filling a separation container through an access port with a suspension. The separation container has a buoy with a tuned density and the suspension can contact the buoy.

The separation container can be centrifuged to cause the suspension to separate into fractions of varying densities. Centrifugation can occur for a period that is appropriate for the suspension, such as about five to about thirty minutes.

The buoy in the separation container is allowed to reach equilibrium within the fluid between two or more fractions. Typically the buoy moves from the separation container bottom to equilibrium within the fractions. In some embodiments, particulates can be concentrated using a guide surface of the buoy. The guide surface can be inclined to an accumulation position 44, 92 near a buoy perimeter location. According to various embodiments, the guide surface can be inclined relative to a buoy sidewall substantially throughout the length of the guide surface. The particulates can be conveyed along the guide surface of the buoy to a collection port. The particulates can be platelets, stromal cells, white blood cells, or the like.

A fraction is isolated in a collection compartment between the guide surface of the buoy and an isolator coupled to the buoy. In some embodiments, there can be a fraction 308 located above the isolator that can be withdrawn prior to withdrawing a first increment of the second fraction 310. In other embodiments, the collection vent tube 203 can eliminate the need to withdraw the fraction 308 located above the isolator prior to withdrawing the first increment of the second fraction 310.

Particulates within the isolated fraction can be re-suspended within the collection compartment by moving an agitator 130, 316 (FIGS. 11A and 19) in the separation container 12 to agitate the isolated fraction to create a more uniform particulate distribution within the isolated fraction. In some embodiments, the agitator is an air bubble 316 that is created by withdrawing the first increment of the isolated fraction 310 from a collection compartment allowing air to enter the collection compartment through the collection vent 58. In other embodiments, the agitator 130 is a mechanical agitator placed in the collection compartment.

The re-suspended isolated fraction can be withdrawn from the collection compartment.

For illustration and for efficiency of use of the system, the various components can be included in a kit 320, illustrated in FIG. 20. The kit 320 includes the fractionation system 10 and a counterweight container 322 if required for centrifuge balance. The kit 320 can also include various syringes 302, 312, and 314 for extraction and application of the fractions and samples. The kit 320 can also include bandages 3226, tape 330, a tourniquet 328, and various additive materials. The kit 320 can include a container 332 for transport and sterilization.

Thus, embodiments of a buoy suspension fractionation system are disclosed. One skilled in the art will appreciate that the teachings can be practiced with embodiments other than those disclosed. The disclosed embodiments are presented for purposes of illustration and not limitation, and the invention is only limited by the claims that follow. 

What is claimed is:
 1. A method for separating a material with a buoy fractionation system, comprising: placing a material in a container having a first buoy portion having a first apex on a first side of the first buoy portion, a second buoy portion having a second apex on a second side of the second buoy portion and wherein the second buoy portion is spaced a distance apart from the second buoy portion, and a third buoy portion interconnecting the first buoy portion and the second buoy portion; and applying a centrifugal force to the material relative to the first buoy portion wherein at least a selected portion of material travels a minimal distance relative to the first buoy portion and the second buoy portion due to a first height of the first buoy portion being substantially smaller than a second height of the second buoy portion, wherein at least the selected portion travels the minimal distance to a volume between the first buoy portion and the second buoy portion.
 2. The method of claim 1, further comprising: withdrawing at least the selected portion from between the first buoy portion and the second buoy portion through a withdrawal port near the first apex that is in fluid communication with a withdrawal passage formed through the third buoy portion and an inlet port from the volume between the first buoy portion and the second buoy portion.
 3. The method of claim 2, wherein withdrawing at least the selected portion from between the first buoy portion and the second buoy portion further comprises withdrawing through a buoy withdrawal passage defined through at least a portion of the second buoy portion that is in communication with the withdrawal port through the withdrawal passage and the inlet port that is defined through a collection surface in the second buoy portion.
 4. The method of claim 3, further comprising: placing a separation container containing the first buoy portion, the second buoy portion, and the third buoy portion in a centrifuge device; wherein applying a centrifugal force includes operating the centrifuge device with the separation container placed therein. 